The former reform minister most recently held one of the top posts in the governing Liberal Democratic Party.

She replaces General Nakatani as defence minister, the second woman to fill the post.

Her support for his goal of revising Japan’s post-war, pacifist constitution risks exacerbating tensions.

“It is important for us to reinforce the Japan-US alliance as well as the trilateral relationships between Japan, the US and South Korea who share the same strategic interests and values,” Inada told reporters.

Reef rows

Tomomi Inada was one of three Japanese lawmakers who are said to have been denied entry to South Korea in 2011 because they planned to visit islands in the East China Sea claimed by both countries.

The South China Sea is another site of potential friction.

Japan has no direct territorial claim. However, trillions of dollars in trade pass through annually, a large amount to and from Japan’s ports.

Tokyo is providing equipment and training to nations like Vietnam and the Philippines, which are most opposed to China’s territorial ambitions.

The US Seventh Fleet, seen by many as Japan’s most powerful adversary in the region, operates from bases in Japan and South Korea.

Japan’s annual defence review, published on Tuesday, warned of “unintended consequences” if China disregards international rules in the wake of a Hague arbitration court decision invalidating Beijing’s claims to most of the sea.